PowerPoint Presentation

Lab 6: Hearing and IllusionsBiology 81L: Human Physiology Spring 20151Visual IllusionsIllusion : describes a situation in which a stimulus leads us to an incorrect perception of the structure that generates it

Perception: our understanding or interpretation of a stimulus

4 types of illusions explored in this labLateral interactionsIllusory contoursAfter-effectsMultistable stimuli

2Lateral interactionsStarting from retina to brain, neurons tend to inhibit or excite their neighbors.

Allows for enhanced contract between similar regions, allowing us to detect tiny differences

Perception: enhancement of contrasttwo area look different in lightness or darkness, but same luminanceObjects with similar orientations seem to tilt away from each other.

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Lateral interactions4Lateral interactions

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We perceive contours (i.e. outlines) that are not actually present. Requires complex neural processing.

Do you see shapes that arent actually drawn?Illusory Contours6After-EffectsInvolves circuits in which opponent population of neurons transmit opposite stimuli

If biased by a strong stimulus, sudden removal of the stimulus momentarily biases the circuit in the opposite direction, producing a phantom perception of the opposite stimulus

7Look at the bulb in the left rectangle for 10 s.Now look at the white background in the rectangle to the right.

After-Effects8Some images cause our brain to flip back and forth between perceptions of their content, although nothing changes in the figureA vase or two faces?

Multistable Stimuli 9Lab 5: Part 1Examine the following 10 illusions and fill in the table in your lab report

10Visual illusions

111Visual illusions

These lines are straight and parallel to each other!212Visual illusions

Which rectangle is darker A or B?313Visual illusions

414Visual illusionsMusician or Lady?

515Visual illusions Kingdom, Yoonessi and GheorghiuThe two images of the tower are identical although the one placed on the right looks to be leaning more.

616Visual illusions

Man, young woman or old woman?717Visual illusions

818Visual illusions

919Visual illusions

1020Bimodal Processing: McGurk EffectThe human brain can combine information from multiple senses to generate a perception

McGurk Effect When there is visual stimuli present, the brain will use it with sound to understand wordsIf the visual information does not match auditory, the visual information will change interpretation of what we are hearing.

21Part 2: Bimodal Processing McGurk Effect http://www.youtube.com/watch?v=G-lN8vWm3m0

22Hearing

23DeafnessConduction DeafnessProblems with structures that conduct sound mechanically

i.e. Eardrum or ossiclesSensorineural DeafnessProblems with converting sound into a neural signal

i.e. Hair cells or vestibulocochear nerveWeber and Rinne tests can help pinpoint hearing problems24Hearing: Weber TestEnd of stem of vibrating tuning fork to foreheadBone conduction to hear sounds in ears. Stimulate cochlea.

Hard to distinguish which type of deafness you have. This test will help point out that there may be a problem

Results: Normal hearing: Equal intensity in both earsConduction deafness: louder in deaf earSensorineural deafness: sound louder in the normal earConduction deafness- problems with mechanical structures of the earHear louder in deaf ear bc vibrating through the bone will stimulate the cochlea.

Sensorineural deafness- problems developing neural signals to the brain- Since we are stimulating cochlea, which has the hair cells that produce neural signal, with sensorineural deafness you wouldnt hear the vibrating sounds. 25Hearing: Rinne TestCotton in your ear. When you cant hear tuning fork vibrating, place end of tuning fork on mastoid boneResults: Normal hearing: Hear vibrating next to ear for 10+ secondsAudible at mastoid boneConduction deafness: Cant hear near ear, but audible at mastoid boneSensorineural deafness:No sound at ear OR mastoid bone Partial hearing loss: Vibrating near ear is audible for less than 10 secondsNotice differences between ears (intensity of the sound)Mastoid process/bone: skull bone behind the ear26Hearing Aids: Structural Problems

Sounds Amplifier

Middle Ear implant: Bypass eardrum, stimulate the ossicles

Ossicle prosthetic

Bone Anchored Hearing Aid: Bypass eardrum and ossicles, stimulate cochlea 27Hearing Aids: Neural Problems

Cochlear Implant: Stimulate sensory neuron

Brainstem Implant: Bypass the whole ear28Audiogram

29Audiogram Example

30Permanent hearing loss31Normal pattern of loss with ageSensitivity decrease with ageHigh frequencies lost firstDecline more severe in men than in womenWomen

Men31Hearing LabHearing threshold: softest sound that we can detectDetermine the threshold for each frequency audiogram

Temporal resolution: how much time is needed between 2 sounds for us to recognize as two distinct sounds? Flip Book example

Spatial resolution: If the same sound comes to you time delayed in different directions, the direction that was first received will be the perceived source of sound (precedence effect)

Masking with white noise : what intensity must a sound be played to be heard over the white noise?

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